The present invention relates to a new and distinct variety of citrus rootstock named ‘UFR-6’. The Plant Improvement Team in Lake Alfred, Fla. has pioneered the development and testing of allotetraploid citrus rootstocks. ‘UFR-6’ (identified as “Changsha+50-7” in field trials) is an allotetraploid somatic hybrid produced by protoplast fusion. ‘Changsha’ mandarin (Citrus reticulata) is the embryogenic suspension culture parent (the source of parental protoplasts) and trifoliate orange ‘50-7’ (Poncirus trifoliata) is the leaf parent (the source of protoplasts).